In recent years, a wireless train control system attracts attention. The wireless train control system performs wireless communication between a train and a wireless base station installed along a track, and performs train operation control and speed control based on information transmitted by the wireless communication. The wireless train control system is advantageous in terms of introduction cost and maintenance cost because a track circuit is unnecessary as compared with a conventional method for controlling a train operation by a fixed block section. Since the wireless train control system can construct a flexible block section which is not bounded by a fixed section, it is possible to increase operation density of trains, which is advantageous also in terms of operational cost.
In the wireless train control system, 2.4 GHz Industry-Science-Medical (ISM) band which does not require a license is often used for wireless communication between the ground and a train, that is, ground-train wireless communication, from the viewpoint of cost. The 2.4 GHz ISM band is widely used also in other systems than the wireless train control system, for example, systems such as wireless Local Area Network (LAN) and Bluetooth (registered trademark). The use of these other systems in trains or in railroad buildings can be a major source of interference for the wireless train control system. Therefore, countermeasures against interference are important in the wireless train control system in order to perform stable communication.
As an example of countermeasures against interference, Patent Literature 1 describes a wireless communication system having a function of monitoring a wireless communication state for the purpose of grasping deterioration of a radio wave environment. Patent Literature 1 discloses a method in which a bit error rate at a time of communication is measured and a warning is given when the measured bit error rate increases to be equal to or larger than a threshold.